He suffered enough so ... yah know the trauma and stuffs that he had but it's not that it's justifying his attitude like being a jerk
I remember in chapter 13 that he gagged after he kissed the teacher. I think he has a split personality where his old self pops out from time to time and his current self (which he doesn't remember anything) is just there most of the time.
I'll just complain in my own language cause this is one of my favorites
Aaaaaaahhhh pugaaaaa kabitin aaaaahhhh shiettttt indi nakooooo haysysysy